diff --git a/crypto/heimdal/lib/sl/slc-lex.l b/crypto/heimdal/lib/sl/slc-lex.l
index 1099ede32b8c..6101569ab602 100644
--- a/crypto/heimdal/lib/sl/slc-lex.l
+++ b/crypto/heimdal/lib/sl/slc-lex.l
@@ -47,8 +47,6 @@ unsigned lineno = 1;
 static void handle_comment(void);
 static char * handle_string(void);
 
-#define YY_NO_UNPUT
-
 #undef ECHO
 
 %}